Sevin Concentrate is not labeled to be used on houseplants, it is only for outside use. Bonide Systemic Granules Insect Control would be good to use for aphids and other listed insects on houseplants.
Yes, you can bring a plant indoors after the application of Sevin Concentrate has had time to dry completely.
You did not mention what Sevin product you are referring to but the Sevin Concentrate product must make direct contact on the fleas for product to be effective per the product label so you would be making applications anytime fleas are present outdoors.
If you are looking to treat inside and outside for fleas, you should definitely get our Indoor/Outdoor Flea Kit. It comes with an excellent product called Onslaught, which is great for both outdoors and indoors. It is also very safe around pets and has a long residual. Also in the kit is an IGR called Martins IGR. It is photo-stable up to 14 days which is about as long as you will find for an IGR that will be outside. Of course you should mix both together in the same tank and apply at the same time both outside and inside.
Sevin Concentrate is only labeled for outdoor use. We suggest using our Roach Control Kits for roaches. You can also use PT Ultracide for fleas. Please take a look at our Roach and Flea control guides for more information.
We would not advise using Sevin Concentrate to treat for bed bugs as it is not labeled for that use or for any use indoors. We suggest looking at our How to Get Rid of Bed Bugs Guide to provide information on what itmes to use and application instructions for a bed bug treatment.