Investing in cryptocurrencies is very risky and of course there are no guarantees,
if someone says that the altcoin is guaranteed to go up in the next few years, of course that is a liar,
because indeed altcoins do not have that guarantee. What can only make prices rise is project development.
This is one of the most obvious signs the project is a scam, after all the developers can only promise to do their best in order for the coin to reach the goals they set for it and hope for the best, however if they promise the project will definitely become successful then you know you are dealing with a bunch of scammers, or at least with developers which have no idea of what they are doing, as it is obvious this is not something anyone can guarantee at all.