3. That board deal with ticket infomation(trains,the moves,sports,etc).
"Walker+" is't sales agency.
In this case,"Walker" stand for 'a person who is going out'.

4. いやずら is dialect expression of "いやです".
'いたずらはいらずら' stand for 'I don't like a mischief.'.
HIROYUKI(tha Web Master of 2ch) like a pun.

(I learn english. if I have mistake,please correct.)