If I didn't file my taxes by April 15, can I still file?

Yes, you can still file and file like normal. If you're due a refund, you don't have to worry about fees because fees are only imposed when you owe the IRS, not when the IRS owes you. If you do end up having a tax debt to the IRS, you'll incur the 5% per month Failure to File penalty for each month you're late (up to a max of 25%) plus the 1% per month Failure to File interest for each month you're late (no maximum on this one).

You can still file a return at any place you could have filed before April 15th. There are a number of on-line places plus some store fronts available. If you would have owed additional tax on April 15th you will now owe that plus a penalty and interest. If you have a refund coming there will be no penalty for filing late.

You can, and are required to file if you made enough money. If you have a refund, there won't be any late fees. If you owe, there will be interest and penalties.

file as you would normally do and if there is a tax liability yes, there will be a 10% penalty

but file asap

Yes, you can file. If you would have owed money even if you had been on time, then you will owe additional money because of lateness. If you would not have owed if you had been on time, then you will still not owe.

You should file for an extension. You have to file your taxes even though there might be penalties for being late.