Is it better to workout (cardio) every other day or 4 days straight.
And I already do strength workout every other day.

If you do both cardio and strength workouts, then it's pretty simple. One day for cardio and the next day for strength workout. Keeps you motivated and more important, you do not overtrain.

...and dont forget to give yourself one day off every week to rest up.

You dont have to do ur cardio on diffrent days. If possible do 20mins of HITT training every morning, and keep ur weight training to the evenings.

You do need to rest, but dont make it a set thing to rest one day a week. Rest when your legs are hurting, untill they stop hurting no matter what days they are. i.e. you may run for 14days in a row and then rest for 4days, or you may run 3 days in a row and take a day off.

Depends on your level of training. I have trained some athletes that only get one day off a week for cardio or skills training(pretty much cardio). Then there are some of my clients just getting started with fitness and twice a week /low impact suffices for now. My training partner (female) used to train and do cardio everyday......there were no signs of overtraining. All depends on your level of training.