It's entirely possible that there is some damage, inflammation or scar tissue that is impinging, irritating or compressing a nerve and that is responsible for the symptoms further down in your calf. It may not be that but there are lots of things that could be going on some pretty minor and others more serious. You didn't say what your original hamstring injury was not what the treatment was and that may make a difference to what could be going on inside your thigh.

It's also possible that the feeling you have of your leg wanting to give way or not responding is due to the lengthy period of limited use or disuse. People are often amazed by how useless their limbs are after even relatively short periods of immobilisation, injury or incorrect use. It can take a long time to recover normal function and it can be a real effort to consciously re-learn functions or movement patterns that you are used to having without thinking about them. Limps in particular can become very habit forming even long after there is nothing wrong with a leg.

There isn't a concept of advanced CRPS nowadays. It's generally divided into acute and chronic but the 'old' concept of different stages where the severity increased with length of time has been largely discredited by increased research. The clinical signs and symptoms and the severity don't necessarily work on a linear pattern so the experienced doctors have long since abandoned the concept of stages of CRPS. In fact, any doctor who does use that concept should be treated with some caution because it would tend to suggest that he or she isn't up to date with the research and latest thinking on the condition.

I am not for a second trying to minimise your problems or suggest you don't have CRPS - I am just trying to highlight that there could be other reasons for some of the problems which might not be so bad so don't get too depressed about it all just yet. Even with CRPS, lack of use of an affected limb can contribute to the symptoms someone has rather than all of those symptoms being caused directly by the CRPS itself.

Hang in there and see what the other doctors have to say. Just one word of caution which is that orthopaedic doctors are not always the best at identifying CRPS - they have usually long since discharged patients and therefore don't see it often. They can also be a bit too happy to find surgical solutions for everything which is exactly what a CRPS patient doesn't need. Don't get panicked into making a rapid decision about anything.