If you don’t claim earnings before 100 rounds pass do you lose those earnings?
No, you don’t lose them. They’ll continue to accrue.
The only thing that happens if you wait longer than 100 rounds is that you will have to submit an additional transaction in order to claim all your earnings. If you wait 200+ rounds you’ll need 3 transactions, 300+ rounds you’ll need 4 transactions, etc. There’s no lost earnings.
is there any way to acess staked LPT if I no longer have access to my metamask wallet?
If you have access to the seed phrase used to create your metamask then you can use that to recreate your metamask wallet on another machine/browser. If you have neither access to the wallet itself, its private key, or its seed phrase, then unfortunately there’s no way to submit the transactions to access your LPT.