<$1m is considered "angel" round, and typically done on SAFEs/notes
$1-4M is considered "seed" round, and is SAFE/note or equity
$5M+ is considered "A" round, and is equity plus normally a board seat
Basically an "investment round" is when you sell equity (and thus set a price) the rest is debt, both legally and practically. If you don't need to file form D you didn't sell anything!
Lots of companies take numerous "seed rounds"; some are continuously funding during the seed stage. They're not out of "seed" until they take a VC round that imposes a valuation on them.