What happens if you cast Animal Growth in constrained environments?

Let´s say a wizard casts Animal Growth (PHB, p. 198) on a lion thus changing the lion´s size form large to huge. – What happens if there isn´t enough space for the lion to grow into?

In the spell description it says:

If insufficient room is available for the desired growth, the creature attains the maximum possible size and may make a Strength check (using its increased Strength) to burst any enclosures in the process. If it fails, it is constrained without harm by the materials enclosing it—the spell cannot be used to crush a creature by increasing its size.

Now I have a couple of questions:

  1. I understand it correctly that the spell takes effect no matter whether or not there is enough space for the enlarged lion to fit in, right?
  2. If there is some enclosure (like e.g. a wall) which the lion fails to break and is then constrained without harm – what exactly does this mean as a consequence? Is the lion squeezed? (Follow up question: If it is squeezed will it have to move to a legal space immediately when it is it´s turn to act? And what if there is no such space for a huge lion anywhere on a packed battlefield?)
  3. What if the enclosure isn´t an object but a creature? Maybe there is an orc standing in the corner of the 15 feet square the huge lion is supposed to fill up. Do the lion and the orc contest the space? Do they make strength checks?

(You get the same wording in the descriptive texts of the spells Enlarge Person and Righteous Might (PHB p. 226 / 273), so my question also adresses these spells.)