1. Is it possible that diabetic medications for increase in insulin levels as oral medicines, injected insulin etc., can cause/result persistant increase in blood sugar levels under certain conditions eg. Pre-diabetic stages, Insulin Resistance etc.?
Barring some kind of gross fault in medication and/or dosage, the answer is no.
2. Is there any relation between common salt & blood sugar?
No direct relation.
Can salt or salty fried snacks taken in excess quantity or accumulated salt can raise blood sugar levels, substancially?
Excess salt consumption can lead to hypertension, which is often associated with increased blood glucose (BG), however if taken with snacks, the increase in lipids is more likely to be the cause. There is a connection between lipids and BG.
Salt & sugar(some other may be as Mg) both seems to be related to water attracting & retaining properties.
A dehydrated condition may lead to raised BG, but excess salt does, somewhat counterintuitively, not lead to dehydration, although symptoms are similar.
It has been noted that taking excess salt/salty snacks in excess raises BS levels after 3/6 days (not instantly) & reversed on reducing salt intake. How it can happen?
The timescale suggests a lipid connection.