All the proceedings with the adoption including "contesting" is all the placing authorities responsibility, because they are the ones who took your LO into care and have responsibilitty for LO
Your own SW and your childs SW should be supporting you with this, and your child's SW should be filling you in with what is going on. Your own SW may not be involved with the court process but should still be a moral support to you!
Know that this is really common . This isn't at all rare, and a large number of BP's will use this last opportunity to object to the adoption. So many adoptive parents are in your position every year. You need to know that the chances of them succeeding would be so vanishingly slight, IMHO you don't need to worry. I can't even think of one case where BP's have got their child back at this stage, with this legal process.
What is happening legally, is that BP's are asking for permission to oppose the making of an adoption order. That's all at this stage, they aren't actually opposing it yet, just asking permission. There's a high likelihood that it's going to fail at this stage, because the judge won't grant them that permission unless they can show they've made changes in their circumstances. Have they really made actual changes to their lives since the placement order was granted? Very unlikely.
In the unlikely event the judge does grant them permission, it then moves on to them actually opposing the making of an adoption order, so more court hearings. I have known this to happen in a few cases with parents I either know irl or read their stories online, yes, BUT still I've not known any birth parents to succeed.
You will be okay. I really appreciate that this is stressful, and worrying for you
But try to view this as simply a delay in the proceedings. It's the birth parents last chance to object, and a huge number of them do, and the chances of it getting anywhere are vanishingly small.
You can perhaps drag a positive out of it - that your LO's birth parents didn't completely walk off, that they did fight for LO - and maybe LO will appreciate that in the future, and feel less abandonned?