4. Switching to lay field and use it (when I open the program the box 'Enable tick offset' is always checked. why? and even if I uncheck it it still shows tick offset highlighted at the top line - not red cross, only green V).
You misunderstand the purpose of "Enable tick offset". It only applies to the lay field and back field bets. It means that if you have set tick offset then it will apply to these bets. If you always want it to work with tick offset then you should leave this ticked and never change it.
Also looked in to log and see than one of the back bet took ages to place. I understand that this is below minimum stake so the action required double time, which should be at least 5-6 sec. but here it took 14 sec.!!!! Why??
It didn't take 14 seconds. You haven't read the log properly. The first item you listed does not actually relate to the following transactions, it is from a previous transaction that was 13 seconds before. Here is an example. See that the final part of the transaction reads "Backed Stags Leap" (not the first part)
1 07/06/2010 18:47:46 11168158766 Below minimum stake, back 2 @ odds 1000 (My bets) OK 155
2 07/06/2010 18:47:46 11168158811 Below minimum stake, update stake from 2 to 2.1 (My bets) NEW_BET_SUBMITTED_SUCCESSFULLY 210
3 07/06/2010 18:47:46 11168158766 Below minimum stake, cancel bet REMAINING_CANCELLED 163
4 07/06/2010 18:47:46 11168158963 Backed Stags Leap @ odds:2.00, stake:0.1 (My bets) OK_REMAINING_CANCELLED 83
one more thing. is it possible to check the log data if a race is no longer exist in market tab? can I check the data from yesterday or 2 hours ago?
Yes, but only while the program is open. When you close the program it does not save this information so you cannot view it from yesterday.