They should officially notify you if your job has gone, yes, but they don't have to give you 'options'. If this new job is a genuine job, does exist, does need doing, you have the skills to do it and has same t&c as your previous job, it's not a question of giving you options, they would just be notifying you that's what's happening.
On return from additional ML you are not entitled to your own job or redundancy, they can move you to a similar job if your old job no longer exists without having to go through any redundancy procedure or consultation.
If on the other hand you don't think this new job really exists - you mention you are not sure why they created it? - that's slightly different. If they have created a post which there is no need for, and no genuine tasks for, then you are redundant, but I can't think of any reason why they would do that - that is clearly more hassle and expense for them to pay you in a non-existent job than actually making you redundant.
If you want to appeal the postponed parental leave you need to ask them for detailed reasons why your absence at any time during the next six months (as they have postponed it for 6 months) will cause undue disruption to the business. That's the key and they haven't explained that to you yet.
So I think it all hangs on whether this new job is an actual job, if there is actually work for you to do. If there is, it does sound like a suitable similar alternative to your previous job, in which case you are not redundant. If not, that's different and you may be.
Seems as though the situation may be that they are not avoiding redundancy particularly, your old role has gone, they have a new one, they were expecting you not to come back and were gearing up for getting someone new in for the new role. Then you didn't resign and instead asked for leave of absence then parental leave. They were advised that you would have to be given the new job if you came back so they have been denying all your requests in the hope that you will not come back so that they can get someone new.
Does that sound possible?