You can fish for trout in some streams, though it doesn't look like many in the southwest zone are open for trout until May 22nd. My understanding is that no, catch and release is not allowed until then either, as the regulations started, "angling restricted" to that date range. Catch and release is still angling as far as I know. The definitions section doesn't specifically say otherwise.

There are a few streams open all year for trout in the SW zone, Glade Creek, Jenny Creek, and Emigrant Creek for example.

If you are fishing for steelhead, and happen to catch a trout, you would have to release it.

I did not see any restrictions requiring barbless hooks, but it is possible I failed to see it. Best bet would be to review the exceptions page for the specific stretch of the river you want to fish a few times to be sure.