This is a known BUG in many TP LINK modems , if modem failed to work after resetting , tp link will provide replacement.:)

Try rebooting your router . there is a black button on rear end push it with a pin or something and then reconfigure it, if the problem persist contact TP LINK support they will replace it. :)

currently w8968 support only 3G , but TP LINK will update firmware for 4G capability . also speed depend on wireless n and not your ISP but still it will be superfast.:)

if you are using android then while entering password for wifi there's option of advance setting . go into advance setting and find dns setting and enter primary dns 8.8.8.8 and secondary 8.8.4.4 try...

YES its possible , you can do it with WDS . search for wds on google , just keep 1st router i.e 8961 nd on 192.168.1.1 and 740n on 192.168.1.2 keep SSID , WIRELESS MODE , CHANNEL , WIDTH same on both...