I have below domains, buying a single wild card certificate beneficial? Or do I need to buy separate SSL certificates.
Do I need to consider anything, when buying the SSL for the above domain. Appreciate your inputs.
Probably a better question for ServerFault or SuperUser, but since you're here, a wildcard certificate will only work for subdomains and only one level deep, so it would not work for any of the examples you mentioned.
Example: A cert with cn=*.example.com would work with a.example.com or b.example.com, but not 1.a.example.com. See https://en.wikipedia.org/wiki/Wildcard_certificate for more details.
Also, when using a wildcard does make it simpler to manage your certificates and renewals and applying updated certs and whatnot because the generation process only has to be done once and the same files and configs can be copied to all servers. Consider though that, if there is some kind of security issue with the wildcard cert, then it would affect all servers that use that cert. So a breach on one server would affect all servers and a problem with one would require an update to all servers that use it.
For these reasons, I generally use wildcard certs for non-production systems, and individual certs for production systems.