1) If your work is good and you demonstrate that you are both easy to work with and can meet the often steep deadlines, age is irrelevant.

Questions 2 and 3 are difficult to determine. It can vastly depend on studio budget and level of ability. Wage can vary quite considerably, so do some research. More importantly you have to take into consideration the expected hours of work, as your time is far more important than money. In this industry your time can become very precious.

4) Like the age question, if you can demonstrate exceptional ability in your portfolio or reel then you should not have a problem. Studios are looking for talent and ability to get the work done, normally in team-based pipeline environments.

Make sure you determine for yourself where in the visual effects field you want to be. Although generalists can be prized in studios, you normally need a specific focus (character modelling, texture painting, matte, technical direction, particle/fluid sim, animator, compositor etc). Generalists do fit smaller studios where everyone takes a share of the work, but if your aim is to work for a larger studio you usually need to be more specialised.