I recommend a Yearly Reset for Alpha or Higher

you need to be in alpha ring 4 or higher

That is definitely odd behavior as the console should not reset on it's own. Is it possible someone else in the house reset it on you? Another possibility is if you had requested to leave the Xbox Insiders program and you were on a higher tier (ie.
Alpha). Your console would be reset to remove any updates that have not been publicly released

You cannot get the OSU for the alpha. You need to unregister the console using the Xbox Insider Hub on Windows 10, then you should be able to reset the console, and download the public release of the dashboard.

Agreed. I would also like to recommend that if you're in Alpha that you head over to the https://www.reddit.com/r/xboxinsiders/ webpage to see if anyone there can offer more help. Alpha and Alpha Skip Ahead are kind of difficult to help with from a support standpoint.

You will need to be a member of the Xbox Insiders to do this.

Unfortunately Avatars is only for Alpha and Alpha step ahead members (which is by invitation only).

If you are still interested though, you can build up your score to go through the different levels by providing feedback on questionnaires and bug reporting.

The more points you get the higher rank you can achieve to get higher placing in the program.

Once you have hit BETA level, give valid and constructive bug reporting and you could be picked for the Alpha or Alpha skip ahead group.

This will take a little time, so dont expect to be in Alpha within a couple of months, most people have been in Insiders for maybe 6-18 months before being picked for Alpha groups.

You do realise that you have to pay to play online on PlayStation. In fact, their yearly price is higher than Xbox, for a much poorer service.