It’s cross, blocking is fine. It is a race, don’t do anything dangerous but be “tactical”
I have attacked before a death spiral because I knew the guy behind was faster through it and I’d have to sprint to catch him afterwards. So I got in first and held him up.
I’ve run up stairs and walked 2 or three steps to let people past. Only when the next section was into a brutal headwind and there was no way I was going to ride on the front of a small group.
However, this is only for places around you. If you are being lapped then get off the line.
But remember when you cross the line it is over, shake hands be nice it is just a bit of fun.