Linking two different domains with one github repository

for simplicity (1) refers to the domain itsmo.co.uk and (2) refers to the domain hyper-epic.co.uk and (3) refers to the domain alias www.revivifygame.co.uk

I have two sites on netlify with two domains.

(1) is linked to my github repository and uses Netlify DNS.

(2) is (manually deployed) which uses an external DNS. Im using an external DNS because the domaiin registrar is Squarespace and they use NS1.

The site linked to (1) has a redirect files and it works. It’s contents is as follows:

htt ps://ww w(3) htt ps://(1)/revivify 301!
htt ps://(3) htt ps://(1)/revivify 301!

I understand i can link (2) with the github repository that’s linked with (1). I probably need to change the redirect file.

In conclusion, I want the repository to be connected with the(2) and i want to change (1) into a manual deployment sites so that there are no redirect issues. Both will host the same site. I also want to add the (3) alias to hyper-epic.

But I want to know in which order i should do things. Let me know. Thanks.

additional info:
(1) is bought from Google domains
(3) from Google domains
(2) from Squarespace

Netlify subdomains:
hyper-epic.netlify.app
https://cocky-poincare-11171a.netlify.app/ (for (1))

Domain Alias:
(3) is a alias for(1) and redirects.

I don’t think there’s any right or wrong order here. You can do it in any order you seem to be comfortable and it would produce the same results.