Everyone has every spell. Survive.

[NichG]

That's easily done. Immediately apply the God Blooded of Vecna template. All knowledge of you immediately fades from the world for everyone except you and Vecna. Proceed to dive into your pocket dimension / mansion / etc. Then you'd only be hit with effects that affect everyone everywhere, and if that sort of wish is possible, it's presumably also possible to wish that you aren't affected by those. It costs some LA, and requires you to undergo torture and lose all your facial features, but that's the cost of assured survival instead of RNG.

Edit: I take it back; there's a much more secure answer. Immediately use Greater Celerity, then Teleport Through Time to go back to before everyone had every spell.

Since archive.wizards is down right now...

Edit2: Since there's a finite amount of people in the world (probably fewer than there are days), even if everyone used Teleport Through Time simultaneously to go back in time, we still shouldn't land in the same year as anyone else, let alone the same month, given there's an infinite amount of years since the beginning of time. Additionally, we don't have to worry about folks going back further than use to lay a trap, as the spell declares how only minor changes in the timeline are possible, so any havoc they could wreak would be very, very limited in scope. This should, at the very least, buy you time enough to make any sort of preparations you want -- such as nesting a demiplane hideaway and encasing yourself in quintessence with contingent spells to wake you at your desired time after you initially teleported.

Material components are tricky for these approaches I think, and a lot of it depends on stuff that's being assumed around the premise. For example, if 'everyone has every spell' but no access to D&D mechanics like levels, feats, etc beyond that unless those mechanics can be granted to you by a spell, then something like 'just take Eschew Components' has a much bigger spin-up loop which might involve pathing through stuff like summoning something that can cast Awaken on you from its own XP (or as an SLA) after PAOing into an animal or tree, just so you can get access to the level system. Teleport Through Time in particular would be annoying to use if you couldn't eschew the components, given the whole 'undisturbed soil' thing.

That said, if there is no specific reason for people in the world to want to kill you in particular, you probably do have much more than one round to escape, especially if we're ignoring any use of Wish that goes off-list (which would bar most 'accidentally kill the world in one round' types of outcomes). So anything that you can do within, say, the first 10 minutes is probably still pretty safe even if you live in a densely populated city. And you probably have a day or more if you live away from other people and don't personally have enemies who would want to kill you.

If we're not ignoring material component costs and people don't automatically get the rest of the D&D mechanics just because of spell access, probably the most dangerous thing that could happen in short order would be people accidentally dropping things like Blasphemy or Holy Word or whatever and killing everyone within 40ft (including themselves though...) - at least, if spells are cast at their minimum allowed caster level.

If everyone is CL 0, no other D&D mechanics, and we're not ignoring material component costs then actually I think it'd probably take months to really get to hellscape levels of ambient danger, because outside of particular people who are already familiar with D&D, it would take active experimentation and analysis to figure out how to actually become capable of casting e.g. enough of a fireball to actually cause harm.