Flat feet. Pain on lower back! Is there a relationship?

Yes, there is. Understand that there is a definite proportional relationship between the human body handling pressure (known as ground reactive force) and lower back pain. If the foot is unable to reduce this force sufficiently due to flat feet, then the "upstream" joints such as the knee and lower back, are unduly taxed.
Yes. Flat feet cause your weight to shift forward which will cause strain on your lower back. Orthotics will help reduce back pain for that reason.
Yes, but... Numbness in the feet can certainly be caused by frostbite. However, there are a spectrum of thermal injuries that can occur due to cold weather. I would be seen by an orthopedic foot and ankle surgeon for this condition. One in your area can be found at www. Aofas. Org.
Yes... A tarsal coalition is an abnormal connection between bones in the hindfoot. Technically, this does not involve the ankle. I would recommend be seen by a orthopedic foot and ankle surgeon. One in your area can be found at www. Aofas. Org.
Yes. Due to different weight distribution when you have flat feet you can end up with back pain as well. Orthotics can help both problems.
Get diagnosis. There may be home treatments for swollen ankles. However, the more important question is why are your ankles swollen. I would recommend that you be seen by an orthopedic foot and ankle surgeon if your primary care physician cannot find the cause of the swollen ankles. Www. Orthodoc. Aaos. Org/foot ankle.
Varied... As with any sport injuries can occur to all tissues of the musculoskeletal system. Things that are common in track are muscle pulls, tendon problems and joint problems. It is important that one has proper physical conditioning as well as strengthening prior to partaking in competitive track and field events.
See an orthopaedist. There are a number of things that can cause pain in theese area of the body. These are very nonspecific symptoms. I recommend that someone pain that is not easily relieved by rest and otc medications be seen by an orthopedic surgeon for a definitive diagnosis. An orthopaedic foot and ankle surgeon would be a good start. One in your area can be found at www. Aofas. Org.
See an MD. This could be due to a number of reasons that may or may not be related to your heel spur. I would seek the attention of a md. You may want to start with an orthopedic foot and ankle surgeon. One in your area can be found at www. Aofas. Org.
Related? This could be any number of things and should be checked out by an orthopedic foot and ankle surgeon. You can find one in your area at www. Aofas. Org.
Other pathology? You may be "favoring" the left foot and putting increased stress on your right. I would get it checked out by your orthopedic foot and ankle surgeon. They may be able to provide you with some relief until your bunion is corrected and you can reestablish a more normal gait pattern. If you are not seeing an orthopedic foot and ankle surgeon one can be found in your area at www. Aofas. Org.
AOFAS. Org. The important thing the initial step is to get a definitive diagnosis. This could result from any one of a number of different pathologies. I would seek the care of an orthopedic foot and ankle surgeon. One in your area can be found at www. Aofas. Org.
Maybe.... There may indeed be a relationship between your problems. However, they could also be independent. I would seek the attention of an orthopedic surgeon. They are the most able to evaluate you from a whole body musculoskeletal perspective. One in your area can be found at aaos. Org.
It is possible. It could be there needs clinical evaluation, acquired flat foot can cause ankle deformity, mal-alignment in leg and therefore gait and postural problems and can lead to back pain - one link there could be others such as congenital / neurological.