Puzzle hunt help

[ApocalypseNowt]

My work have sent out another puzzle hunt for us to have a go at during lockdown (if we want to obvs). There are 5 stages and you need a password to get onto the next stage.

The first stage is 27 pictures of landmarks - I think i've managed to identify all of them but haven't got a clue as to how to work out the password :(

All of the pictures are bordered by colours (green, red, orange, yellow or blue) so I think that may have something to do with it?

Anyhoo, any ideas welcome as I'm stumped!

I'll try and put pics of the landmarks on here. These are what I think they are:

leaning tower of piza
eiffel tower
hagia sophia
burj khalifa
gateway arch
sydney opera house
petra
pantheon
machu pitchu
st basils cathedral
space needle
cn tower
one world trade centre
potala palace
colloseum
brandenburg gate
dome of the rock
forbidden city
pentagon
flatiron building
angkor wat
winter palace
shard
taj mahal
rialto bridge
griffith observatory
brooklyn bridge

@DanFMDorking if you want a clue (or the answer) for stage 2 let me know. I could REALLY do with a hand on stage 3......

@ApocalypseNowt - yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes, yes please

@DanFmDorking so for the second puzzle you just needed to work out the key. I concentrated on the two 3 letter words as I guessed one of them would be 'the'.
NWD wasn't making sense but if we say BPM is THE then fill in the rest of the alphabet that gives you the key. E.g. if B = T, then C = U, D = V and so on.
The solved phrase is " Stay alert, control the virus, save lives. Password for the next stage is heroes"
So 'heroes' in the password!

Hope you're sitting down when you see what stage 3 is.....!

I've solved meta 5 but am struggling with the rest

What is stage 3?!

Will post stage 3 when I'm back at my desk!

Next stage is meta puzzles (meta...Latin for really mean). Basically you have to solve all of them to unlock the password for the next stage. I've done one, here are the next 3.

For info the bold type on the first pic is what I've put in so far

More meta

What the actual???

Should've known. There was a meta round last time too

I think these are for people who think 'Only Connect' is a piece of piss.

The U2/Neil Young answer is Silver and Gold - 47+79.

Thank you @PatriciaHolm !! I'll check the final answer in the morning

I've got a bunch more of the crossword clues, trying to figure out what to do with them!

Bugger. Tried adding all the atomic numbers but answer not working. Bugger bugger bugger.

I'm going to leave that one on the back burner for a bit. I'm sure the answer will come to me 😬

Onto meta 2. I've worked out these are American state capitals but have no idea what the numbers on the left are for. Hmmm...
Think the first answer is decade and the last hind.

Have got the answer to meta 2! It's US Capitals. Yay for random guesses

I've done the dominoes. Won't post unless you ask as that one is just logic, they tell you what to do!

@PatriciaHolm I must be missing a trick! I tried to follow the instructions but my answer wasn't right. Tell me or message me pleeeeeeeeease

Dominoes? I get 6480...

I have most of the crossword clues but I seem to have 3 x11 letter words and 2 x10 , whereas it should be the other way round. And the film isn't Flashdance ;-)

..and I don't think the radio frequency is 96...

Ta! I will check

Dominos one is correct - thank you!