There are slight rules difference between 1 and 2 (the non-Fight mechanics were overhauled for 2, there's only a single moveset in 1 and there's clarity around ties introduced in 2) and Character Creation and the scenario were refreshed in 2. If you have Transgender Deathmatch Legend II I'd say the original game isn't a necessary purpose unless you're interested in seeing how things developed.
The something exclusive is just in Itch's phrasing for Rewards, which is where community copies are implemented, there's nothing extra from claiming a copy.