I'll reply all three straightly; if you want to invest in bitcoin, use your spare money. Not just Bitcoin; anything that has to do with the word invest. Also, it depends on the country where you are staying. Some countries have banned crypto, and using it is like looking for trouble, you may loose all your funds when they catch you, so I suggest you check the status of your country and know if they accept their citizens to use crypto.

Finally, I wouldn't really count bitcoin as a store of value (just in case you want to use it for this). Bitcoin's volatility makes it unworthy for that. There are stable coins like usdt where you can store your money and it will have it's fixed value without the ability of crashing down.

The reason i prefer to invest in bitcoin is because it's self moderated and bitcoin regulate itself without the help of anyone, and again bitcoin investment can multiple wealth and it has a higher security level, which no one can thief your coin without been known your login details, it's the reason why i prefer cryptocurrency investment than manual investment, but people dislike cryptocurrency because its online and don't really understand its concept.

this is one of the positive functions of bitcoin or in a good sense, but you also have to know what impact we will get from investing here and of course there are some impacts that other people, especially people who are just starting to invest here, don't know yet.
as we all know here that this bitcoin investment does not guarantee you will get a big profit, it could be the other way around if you don't know the function of bitcoin and you are wrong in taking a position (buying at a high price) you may lose money you because here is a very risky place. and many new people who have been affected by bitcoin because they don't know and are just trying to follow the investment here by hoping that bitcoin will continue to rise and not be accompanied by patience and the results are predictable. when bitcoin went down like now many people complained and felt they lost their money and stopped investing even though this was the wrong decision.
so be careful especially for you beginners because here it is not only investment and instant profits but also you have to be patient and smart in seeing the situation because this is a risky place

why we all invest in bitcoin, because considering that no other investment provides the same security and benefits as bitcoin, bitcoin has been evolving for a long time, and bitcoin can be trusted because there are no third parties, unlike other investments that involve multiple third parties. three, in the end, if we invest elsewhere, once we invest our money, they run away..

Your information is correct upto a certain extent OP.
But i guess these reasons are not only restricted to BTC only, rather this applies to other alt coins too.
Moreover for me the main reason to buy the coin is it’s price and scope.
Many Traders have already predicted that BTC will change the crypto world soon in the future, and therefore i am buying the coin whenever i have some money to spend.
Hope OP i have added a little extra info for you to debate upon.

That's how the economic principle works, when demand is high and supply is limited, prices will increase. how important it is to understand well what you are going to invest in. regardless for long or short term, we should know it well. With a combination of technical and fundamental analysis, you can get a great opportunity to take profit. even if you don't have the ability to do market analysis, then use a way to save, and see what you will get a few years later.

this decade is enough to prove that btc has great potential. although in the future the price will continue to change, it can again make new record highs or lows. so be prepared with all the risks. Keep in mind that big profits are always accompanied by big risks.

There will still be those people, institutions and government that cannot see the full potential of bitcoin in this modern generation. But to us who have a background of it and understands well about its features and having a limited supply.
We all shall see the true potential that it can give to those who will start bagging it.

My reason to invest in bitcoin is because bitcoin has been survive since 2011 and the price is keep rising every single year, i know my reason is very simple but for me this is the important thing for me to invest on bitcoin.

Investing in Bitcoin is one of the best thing to do in terms of savings money and the reason is that Bitcoin is not a paper money to spoil and it adds value even while saving it, it can't be Freezed by any bank or government. Hence it should be taken as an advantage....

Bitcoin is the king of Cryptocurrencies, and despite getting it banned in some countries, it still remain strong and unstoppable. Bitcoin have less security risk. It also profitable Investing in Bitcoin, but that is, if the Investor is patience enough. Bitcoin is decentralized, it is not controlled by any organization or government. I must admit, bitcoin is and have been a good Cryptocurrency to invest in.