B737 First Officer reported an airspeed disagree during two takeoff attempts. Flight crew rejected during both takeoff rolls and returned to gate for maintenance.

Narrative

Aircraft X was a flight that was cancelled the day before due to a MX (Maintenance) issue. parts (flap track and nose wheel tire) flown in and repaired that morning. New Maintenance Release was issued. We boarded and pushed back normally. After pushback I started both engines. Had a normal start on number two engine. After light off and during spool up just and the end of the start cycle an ENG (Engine) light illuminated on master caution. I brought it the Captains attention. We both looked up to discover both engines had reverted to the ALT control mode. We contacted Maintenance Control and were instructed to select ALT mode then back to normal. That cleared the error; and we were cleared to continue no write up necessary. We got our clearance and were cleared for takeoff. During takeoff role Tower gave us an amended clearance. The clearance was to climb to 2;500 or at 7 miles before turning left on course for noise abatement. This caused a distraction because at the time with the workload of the takeoff; accent of the controller; and the unexpected last-minute instruction both the Captain and I didn't understand the instructions clearly. I originally thought the controller stated to climb to 2500 and 7 miles to turn on course. While the Captain was asking the controller to repeat in looked inside the aircraft pointe at the MCP (Mode Control Panel) and said 'set 2500' I figured we could as further clarification airborne. While I looked at the MCP I noticed there was an airspeed disagree message. My airspeed was at 80 knots and accelerating the Captains was at 100 knots. I stated the observation and went heads outside again and then the Captain called for a reject and took over aircraft control. Once the Captain took control; I noted the speed on his was 110 knots where mine was indicating 90. I then notified the Control Tower of our abort and then made the remain seated PA. After performing the QRC followed by the QRH the Captain suggested we call for the fire trucks to check the temps of our brakes. I contacted Tower to request this (not sure of my wording) but the Tower acknowledged. After discussing the brake cooling chart both the Captain and I felt it was safe to continue back to the gate. I requested this with the Tower and recall asking about getting the brakes temps checked again being I saw not response from fire rescue and wanted them to know we were returning to gate. The Tower did acknowledge and kept asking if we saw the marshallers. Which we did not see yet. Once the marshallers got into position; we notified the Tower and were cleared to proceed to gate area. Stairs were brought to the aircraft and Maintenance came on board. Fire rescue never did respond. I asked the Tower if they had fire rescue on the airfield and I was told they did. I asked why they never showed up and Tower asked me to standby and then I never heard from that person again. Maintenance worked on aircraft for approximately 4 hours; and we were once again cleared for departure. During the second attempted takeoff I ask the controller if he wanted the same noise abatement before taking off and got that clearance before we started the takeoff roll. This time we spotted the error quicker and aborted at a much slower speed (40kts). This time Tower asked us if we need fire rescue; and we declined due to the low speed.