So whats with this "merge" items ballache? I'm a member of the ocuk clan but never played this co op
lol, I'll quote your original post and try to explain things in plain english since you seem quite confused.
I've always enjoyed D3 and worked my way through it in single player on normal & started the RoS expansion and have a level 42 character however there's some bits I just dont get so if anyone can advise that would be great...
1. Are seasons a case of starting a new character, and is that character only available for that play through?
2. If I change the act with my character will I lose my current save point in Ros?
3. Is it best to start a new character & new season to access the diablo 1 tribute? (I just had a quick go at this & couldnt see a portal in the old ruins but maybe I need to do something else first?).
It really doesn't matter, I did this on normal mode (non season) as it was available before the season started.
4. I've always fancied playing this with others or some of you guys in the ocuk clan but do I need to get to level 70 or something extreme first?
Seasons last approx 3 months in time where players start the whole Diablo experience from level 1 with no items, no items from your personal stash or gold that you may have in normal mode (sometimes called non season). Currently we're on Season 9 where each season offers vanity rewards as an incentive to lure players in such as a Pet, a character portrait, cosmetic wings, transmogrification, extra personal stash tabs etc which can only be earned by participating in the season and progressing through the seasons objectives (via a seasonal journey which will eventually unlock the rewards).
Each character you create whether in season, normal, hardcore etc will have its own progress throughout story mode, you can go back and return to your current point anytime you wish via the main menu.
The OcUK clan is quite frankly populated with between 0-3 players whenever I was in it (which was for many months, maybe a year+) I'm fairly certain most people who have replied lately aren't apart of the OcUK clan. The only note worthy person I know who is in OcUK is Caphel and he hasn't logged on for almost a month. I do strongly suggest finding a clan where you can ask these questions whenever you need and can get quick answers.
Here is a link to the Clans, Communicites and Friends section on the Diablo Forums
https://eu.battle.net/forums/en/d3/4338510/
Also just to add. The "merge" item comment simply means that at the end of each season your seasonal character will become a normal mode character and all of it's items, gold, etc will be transferred over via in game mail (bottom left of the screen). Sometimes players will have for example a Demon Hunter with a set of gear, and when a Seasonal Character has the same set of gear players then need to look at both sets of gear to determine which items are best as in many cases you will end up with the exact same items but with different stats.