Apply scale and fade effect to Images together
Try

String command2="ffmpeg -i /sdcard/videokit/input.mp4 -loop 1 -t 2 -i /sdcard/videokit/first.png -loop 1 -t 2 -i /sdcard/videokit/second.png -filter_complex "[0]boxblur=enable='lt(t,2)+gt(t,10)'[vid];[1:v]format=rgba,fade=in:st=0:d=0.5:alpha=1,fade=out:st=1.5:d=0.5:alpha=1[img1];[2:v]format=rgba,fade=in:st=0:d=0.5:alpha=1,fade=out:st=1.5:d=0.5:alpha=1,setpts=PTS+10/TB[img2];[vid][img1]overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2[bkg];[bkg][img2]overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2" -preset ultrafast -c:a copy /sdcard/videokit/output.mp4";