ATH | Leverage | Index Funds and more

I got a few questions as a newbie

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1. Some of the companies I want to invest long-term are either at their ATH or close to ATH, like Microsoft or Nvidia. I'm wondering whether I should wait for it to drop, because most of the stock market is green this year, so I have a feeling it may drop since it grew so much, what do you think? Some of it just recovered from 2022 to it's pre-2022 state, but Nvidia has 205% growth this year, which is crazy
2. Index funds – the legendary S&P 500. Everyone says it's the most stable etc – but I've found other indexes with even better growth. SP500 usually have the 7-10% yearly return and last 5 years went up 56%, but for example the INDEX Vanguard Growth ETF went up 87% for the last 5 years – and it was also a steady growth, not a lucky spike during one period. What do you think, is it really smart to go with SP500 or are there other ones that are much better, even tho SP500 is so hyped by everyone? and if you agree – what other indexes with better return would you recommend?
3. Leverage – I'm not familiar with how much can you leverage in stocks, but for people that invest in the top 10, which most likely will go up in the future, wouldn't be smarter to invest it with i.e 5x leverage, since the companies like Microsoft are stable, and eventually will grow?
4. Stock Math – let's say I invest $10.000 in a stock and it declines -50%. I know have $5.000. If it goes up by 50%, do I get $7.500 or do I get my $10.000 back? Logically the first answer, but something doesn't give me a peace of mind here, so I prefer to ask
5. Eli Lilly – what do you think about this stock? Growed massive amount lately, and pharmaceutical industry will definitely be there in 5 or 10 years.