Can a coin have let's say 1 Decillion? Would this affect the coins stability in any way?
In theory the amount of coins limitless, but if you try to raise the limit too high, you'll encounter some issues (like integer overflows at various point in the codebase) that bitcoin/litecoin devs have not anticipated.
Basically, with current codebase, about 92 billion is the maximal safe amount of coins. If you want more, you'll have to fix/workaround the code (like using 128bit integers, or having the coin less divisible than 1 coin = 100 million satoshis) or be prepared for trouble - some of the flaws may be just wrong numbers, some of them may cause mayhem and kill the coin